Propagation of the Colombian genotype of cacao (Theobroma cacao L.) CNCh-12 by somatic embryogenesis

Abstract

Cocoa production (Theobroma cacao L.) is essential globally and constitutes one of the leading export products for Colombia. Understanding the limitations faced by this crop in Latin American countries, it is required, among other aspects, to contribute to strengthening the first link in the production chain through efficient propagation methods and genetic improvement. Knowing that somatic embryogenesis is an alternative to conventional propagation and constitutes an obligatory step in a breeding platform, the objective of this work was to establish a somatic embryogenesis protocol until the plantlet acclimatization in the nursery for the regional genotype CNCh-12, a promising material with productivities higher than 2,000 kg/ha. Different protocols were evaluated, from callogenesis induction, through the expression of primary somatic embryos (PSE) followed by maturation and subsequent conversion to plantlet two types of explants (petal and staminode) and culture time (according to the stage). Additionally, the induction of secondary somatic embryos (SSE) was evaluated in two culture media (L and F). For CNCh-12, the petal was found as an appropriate explant, with a minimum time of 15 days in induction for PSE formation, without difference between the culture media F and L (22 average embryos). Embryo maturation was achieved in medium F after 30 days, followed by an additional 30 days for conversion to plantlet (52.83%). The concentration of salts to increase the conversion and development of the embryos was 1/5 of that used in F. The highest number of SSE was in the L medium. Finally, the ex-vitro adaptation was achieved when the plants were planted in 50:50 sand-coconut fiber and moistened weekly with Hoagland's solution (1:10). Keywords: Cacao, petals, in vitro propagation, plant growth regulators, somatic embryogenesis.